Factors affecting the liquid ammonia level when it is separated by a tank
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During the construction phase of our facility, ammonia was introduced into the refrigeration system using the KBR process, and the tank for storing liquid ammonia is designated as 149D. When the ammonia concentration is brought to 50%, it is isolated to maintain liquid level and pressure. But the weather has been a bit hot during this period, causing the liquid level to fluctuate periodically; it rises to around 30% during the hot days and drops to around 3% at night when it’s cooler. This phenomenon has been occurring periodically for several days now. Could everyone tell me what the reason for this is? How can it be explained?
This is quite normal; liquid ammonia is highly affected by changes in temperature.
The occurrence of this phenomenon indicates that the insulation layer of your liquid ammonia tank is not properly designed; as the temperature changes, the pressure and liquid level of the liquid ammonia inside the tank change as well, resulting in significant fluctuations in the liquid level during the day and at night.
I also know the relationship between liquid level and weather temperature, but I think it is when it’s hot during the day that liquid ammonia flashes, causing the liquid level to drop； When the weather is cold at night, it is correct for the liquid level to be high. And now the situation has reversed: the liquid level is around 30% during the day, but only around 3% at night.
The insulation work on our equipment has been completed, including the connected pipelines, which have also been properly insulated. What other possible reasons could there be?
Personally, I believe that temperature has an impact on the liquid level, but it shouldn’t be that significant. There could be several reasons for this: firstly, a problem with the level gauge itself, incorrect parameter settings within the DCS, or amplification of changes when pressure is converted into a liquid level reading (one can refer to the on-site level gauge to determine whether there is indeed such a large variation in the tank’s level gauge). Another reason could be the entry of oil into the tank, which causes changes in the liquid level (by comparing these changes with the initial level)
You can check the actual liquid level on site and compare it with the DCS liquid level to determine if there is a problem with the transmitter. Changes in liquid level are related to changes in temperature, but they may also be due to distortion in the liquid level transmitter.
I have confirmed that the level at the site matches the level shown on the DCS, so the possibility of a loose level gauge being the cause can be ruled out.
May I ask what type of level gauge is being used?